Rust

Add special case for `afl-addseeds`'s `--help` flag #835

Job	Run time
lint	1m 9s
build (ubuntu-latest, stable, cc)	3m 12s
build (ubuntu-latest, stable, clang)	2m 9s
build (ubuntu-latest, nightly, cc)	2m 52s
build (ubuntu-latest, nightly, clang)	3m 47s
build (macos-latest, stable, cc)	3m 21s
build (macos-latest, stable, clang)	4m 11s
build (macos-latest, nightly, cc)	3m 42s
build (macos-latest, nightly, clang)	2m 50s
all-checks	1s
	27m 14s

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